1. Field of the Invention
The present invention relates to a universal, modular, temperature controlled MRI phantom for calibration and validation for anisotropic and isotropic imaging which may include hollow fluid filled tubular textile-based MRI phantom for calibrated anisotropic imaging.
2. Background Information
This patent describes a technology innovation that could provide better calibration of brain imaging for brain trauma that impacts an estimated 4 million US citizens annually an estimated 300,000 veterans from recent military conflicts that have had brain trauma and potentially traumatic brain injury (TBI).
MRI
Since inception in the 70's, Magnetic Resonance Imaging (MRI) has allowed research and diagnostic imaging of humans and animals. MRI involves using a combination of high strength magnetic fields and brief radio frequency pulses to image tissue, typically by imaging the dipole movement/spin of hydrogen protons. MRI has long provided two and three dimensional imaging of internal tissue, tissue structure, and can provide imaging of functioning processes of tissue called “Functional MRI” or fMRI.
Diffusion MRI (or dMRI) is an MRI method or technology which allows the mapping of the diffusion process of molecules, mainly water, in biological tissue non-invasively. Since the earliest developments in the 80s, diffusion MRI, also referred to as diffusion tensor imaging or DTI, has seen extraordinary advancement. Diffusion tensor imaging (DTI) is important when a tissue—such as the neural axons of white matter in the brain or muscle fibers in the heart—has an internal fibrous structure analogous to the anisotropy of some crystals. Water will then diffuse more rapidly in the direction aligned with the internal structure, and more slowly as it moves perpendicular to the preferred direction. This is a well developed area of MRI research with several text books on these points, such as Johansen-Berg H. Behrens T. E. J., Diffusion MRI: From quantitative measurement to in-vivo neuroanatomy London Elsevier, 2009, and Jones D. K., Diffusion MRI: Theory, Methods, and Applications, New York: Oxford University Press, 2010.
The advanced work in MRI is also permitting highly detailed neural pathway mapping, sometimes known tractography or fiber tracking. Tractography or fiber tracking is a 3D MRI modeling technique used to visually represent neural tracts (or other biologic tracts) using data collected by DTI. Recent textbooks applying the methods to map white matter pathways include Oishi K., F. A. V., van Zijl P. C. M., Mori S., MRI Atlas of Human White Matter, Amsterdam: Elsevier, 2010 and Catani M, Thiebaut de Schotten, M, Atlas of Human Brain Connections, New York: Oxford University Press, 2013.
One MRI technology is known as high definition fiber tracking, or HDFT, and is used to provide extremely highly detailed images of the brain's fiber network accurately reflecting brain anatomy observed in surgical and laboratory studies, as discussed in a report from the University of Pittsburgh, School of Medicine in the August, 2012 issue of Neurosurgery. The findings of this report show that HDFT MRI scans can provide valuable insight into patient symptoms and the prospect for recovery from brain injuries, and can help surgeons plan their approaches to remove tumors and abnormal blood vessels in the brain. One author Juan Fernandez-Miranda, M. D., assistant professor, Department of Neurological Surgery, Pitt School of Medicine, noted that “in deep brain surgery, the neurosurgeon may need to cut or push brain fiber tracts, meaning the neuronal cables connecting the critical brain areas, in order to get to a mass.” adding that “HDFT is an (MRI) imaging tool that can show us these fiber tracts so that we can make informed choices when we plan surgery.” Co-author of this report and co-inventor of the present invention, Walter Schneider, Ph.D., professor, Learning and Research Development Center (LRDC), Department of Psychology, University of Pittsburgh, who led the team that developed HDFT has elaborated that “a sophisticated MR scanner is used to obtain data for HDFT images, which are based on the diffusion of water through brain cells that transmit nerve impulses. Like a cable of wires, each tract is composed of many fibers and contains millions of neuronal connections. Other MR-based fiber tracking techniques, such as diffusion tensor imaging, cannot accurately follow a set of fibers when they cross another set, nor can they reveal the endpoints of the tract on the surface of the brain.” The instant application references the work discussed at the Schneider Laboratory at the LRDC (http://www.lidc.pitt.edu/schneiderlab/) for further background on the advancement, current status, and potential of anisotropic imaging and fiber tracking techniques with advanced MRI technologies, which work forms the background for the present invention.
Using advanced, non-invasive, in vivo diffusion imaging techniques combined with HDFT analysis and visualization, the Schneider Laboratory advances clinical research in the diagnosis and treatment of neurological pathology and trauma. The Schneider Laboratory works with the Neurological Surgery Department at UPMC to visualize fiber tracts within the brain in three dimensions in order to plan the most effective and least damaging pathways of tumor excision in patients suffering from various forms of brain cancer. Additionally, the Schneider Laboratory has been engaged in a Department of Defense and Veterans Administration funded HDFT projects to localize the fiber breaks caused by traumatic brain injuries (TBI), which cannot reliably be seen with the then current standard computed axial tomography (CAT or CT) scans or then available MRI scans in mild traumatic brain injury (mTBI), aiding the diagnosis and prognosis of patient brain trauma.
Others have developed fiber tracking technologies using MRI based scans. Consider, the S. Mark Taper Foundation Imaging Center at Cedars-Sinai which offers diffusion tensor imaging (DTI) fiber tracking and functional (fMRI) motor mapping using magnetic resonance imaging fused with 3D anatomical image of a brain to aid in surgical planning.
U.S. Pat. Publication No. 2006-0269107, now U.S. Pat. No. 7,529,397 developed by Siemens Medical Solutions USA, Inc. discloses methods for automatically generating regions of fiber tracking seeding points in diffusion tensor images.
The Johns Hopkins University's U.S. Pat. No. 8,593,142 discloses a system and associated method of automated fiber tracking of human brain white matter using diffusion tensor imaging.
U.S. Pat. Publication No. 2006-0165308 discloses a neighborhood relevance component that considers diffusion tensor matrices from neighboring pixels or voxels.
U.S. Pat. No. 8,076,937, developed by Koninklijke Philips Electronics N.V. of Eindhoven, NL, discloses diffusion data processing apparatus comprising a “segmenter” arranged to segment the diffusion tensor data according to at least one segmentation model representing at least part of a fiber bundle.
U.S. Pat. Publication No. 2007-0124117 discloses a system determining a direction of tracking a fiber based on a vector corresponding to a largest value of a set of values for a tensor.
U.S. Pat. Publication No. 2013-0279772, developed by BrainLAB AG of Feldkirchen, Germany (BrainLAB), discloses a method for finding fibers in image data of a brain which matches a functional atlas of the brain to an image data set which represents a medical image of the brain; performs functional atlas segmentation in order to segment the image data set into functional areas; and uses the segmented image data set to determine at least one seed point for a fiber tracking algorithm; and performing fiber tracking in order to find the fiber.
MRI Phantoms
As advanced MRI systems and technologies are developed, tested and/or placed in operation, the accuracy of the technology must be verified or validated. Validation may be defined as process wherein the accuracy of the technology/imaging algorithms is proven or verified. Further, the accuracy of the associated system must also be periodically verified (i.e., MRI system calibrated—also referenced as Quality Control aspects) to ensure original and ongoing accurate results and safe operation of the MRI systems. Generally speaking, calibration and/or test measurements for an MRI system are performed using an imaging phantom or more commonly referenced as a phantom. A phantom is any structure that contains one or more known tissue substitutes, or known MRI signal substances, forming one or typically more test points, and often is used to simulate the human body. A tissue substitute is defined as any material that simulates a body of tissue. Thus a phantom may be defined as a specially designed object that is scanned or imaged in the field of medical imaging to evaluate, analyze, and tune the performance of various imaging devices. A phantom is more readily available and provides more consistent results than the use of a living subject or cadaver, and likewise avoids subjecting a living subject to direct risk.
Numerous phantoms have been developed for various imaging techniques. For example, U.S. Pat. No. 6,744,039 relates to a fillable phantom which includes a container, a porous medium within the container, and a connector for filling the container with a radioactive solution.
U.S. Pat. No. 6,720,766 relates to a thin film phantom for testing and measuring the performance of magnetic resonance imaging (MRI) and x-ray computed tomography (CT) imaging systems. The phantom includes a planar medium and a plurality of individually sub-resolvable scatters having preselected magnetic resonance properties within a pattern of resolvable regions on the surface of the medium.
U.S. Pat. No. 6,409,515 describes a phantom which includes a plurality of segments having unique identifiers, the segments joining together to form a polyhedron around an inner plate.
Electronics and Telecommunications Research Institute's U.S. Pat. No. 7,667,458 discloses a phantom for Diffusion Tensor Imaging (DTI) to measure the main physical quantities of diffusion tensors, such as diffusion anisotrophy, a diffusion principal axis and a route of the diffusion principal axis, and to evaluate the accuracy of DTI. The phantom for diffusion tensor imaging includes: an outer container providing a space; materials for diffusion measurement located in the space of the outer container and formed of bunches of micro-tubes; and materials for fixing located in the space of the outer container to fix the materials for diffusion measurement to a specific location. The micro-tubes in this phantom design may be stems of various plants such as leaves of vegetables or a bamboo stem.
The Medical College of Georgia Research Institute, Inc.'s U.S. Pat. No. 8,134,363 discloses a phantom for use with diffusion MRI comprising a plurality of anisotropic arrays stacked in a plurality of parallel rows to form a macro-array, wherein each of the arrays includes a plurality of typically glass capillaries (ID 10-90 microns) with each of the capillaries holding a first fluid; and a housing, holding a second liquid.
U.S. Pat. No. 8,643,369 describes an anisotropic diffusion phantom for the calibration of any diffusion MR-DTI imaging sequence the form of an array of thin glass plates separated with H2O layers, wherein the layers have a thickness of about 10 microns.
BrainLAB's U.S. Pat. Publication No. 2006-0195030, now U.S. Pat. No. 7,521,931, discloses a phantom for use with diffusion tensor imaging which includes a container and a plurality of structures within the container. The structures have anisotropic properties, wherein when the phantom is subjected to diffusion tensor imaging, the structures provide data that is recognized as fiber bundles. The structures can be formed, for example, from cloth tape, silk, wood, glass fibers cord (synthetic and viscose) and/or “microfibers”.
The Department of Health and Human Services published U.S. Pat. Publication No. 2012-0068699, which discloses a phantom calibration body for calibrating diffusion MRI device which includes a homogeneous aqueous solution that contains a mixture of low molecular-weight and high molecular-weight polymers housed in a container.
Alexander J. Taylor, “Diffusion Tensor Imaging: Evaluation of tractography algorithm using ground truth phantoms,” Virginia Tech, May 2004 describes the creation of a physical phantom to evaluate the performance of tractography algorithms, which are used to estimate tissue microstructure. In creating this phantom, Taylor used polytetrafluoroethylene (PTFE) capillary tubing with an inner dimension (ID) of over 300 microns and an outer diameter of over 700 microns. Multiple segments of the tubing were cut, filled with water, and assembled into sheets with a 90 degree crossing pattern. The capillary sheets were placed in a small plastic container and surrounded by gelatin to mitigate air related susceptibility artifacts in the images.
Ching-Po Lin, Van Jay Wedeen, and Jyh-Horng Chen, “Validation of diffusion spectrum magnetic resonance imaging with manganese-enhanced rat optic tracts and ex vivo phantoms,” Neorolmage, vol 19 (2003) 482-495, discusses creation of a phantom to be used to compare the effectiveness of DTI and Diffusion Spectrum Imaging (DSI) for correctly determining the orientation of crossed axonal fibers. Lin used PTFE “microbore” tubing with ID 50 micron and OD 350 micron. Segments of the tubing were filled with water and assembled into sheets. Layers of these sheets were stacked at 90 and 45 degrees in reference to each other in an interleaved fashion. The structures were then secured to a firm plastic plate.
Elisabeth A. H. von dem Hagen and R. Mark Henkelman, as described in “Orientational Diffusion Reflects Fiber Structure Within a Voxel,” Magnetic Resonance in Medicine, 48: 454-459 (2002), were possibly the first individuals to evaluate the effectiveness of DTI for determining fiber orientation using a physical model. This phantom also consisted of PTFE “ultramicrobore” tubing having ID 50 micron and OD 350 micron. The capillaries were filled with water by a gluing a 22½-gauge needle to each segment. After being filled, the capillaries were sealed by melting both ends and removing the needle. The capillaries were placed in three different orientations, namely, aligned, coiled, and random and placed inside borosilicate glass tubes. For discussion of similar phantoms see Atiba Fitzpatrick, “Automated Quality Assurance for Magnetic Resonance Image with Extensions to Diffusion Tensor Imaging” Virginia Polytechnic Institute, June 2005.
Lorenz, R., Bellemann, M E., Jenning, J., & Il'yasov, K A., Anisotropic phantoms for quantitative diffusion tensor imaging and fiber tracking validation (2008). Appl Magn Reson. 33, 419-429, disclosed work from the University Hospital Freiberg, Freiberg D E and University of Applied Science Jena, Jena D E, in which four different types of fiber phantoms were used, namely Hemp, Rayon (Diameter 100 Microns), Linen (Diameter 340 microns), and Dyneema (Diameter 200 microns), wherein Dyneema is formed of braided strands of polyethylene fibers. Each of the fibers were used to form fiber bundles under water with the bundle having a cross sectional area of about 450 mm2. Crossing phantoms for similar bundles were formed in a frame and tested. The conclusion of the study was that only the Dyneema bundles served as reproducible phantoms, but these only allowed tracking of the interstitial water due to hydrophobic properties.
Poupon, C., Rieul, B., Kezele, I., Perrin, M., Poupon, F., & Mangin, J F. (2008), New diffusion phantoms dedicated to the study and validation of high-angular-resolution diffusion imaging (HARDI) models. Magnetic Resonance in Medicine, 60, 1276-1283; discloses work developed in part at General Electric Healthcare and Institut d'Imagerie Biomedicale in Gif-sur-Yvette France and utilized 20 micron diameter acrylic fibers bundled together in a two part frame forming a 45 degree and 90 degree crossing phantom and in a fiber density of 1900 fibers/mm2.
The current needs for MRI phantoms for anisotropic imaging for validating and calibrating fiber tracking technologies and systems were also recently elaborated in the May 2014 International Society for Magnetic Resonance in Medicine (ISMRM) meeting, see Michael A. Boss, Thomas L. Chenevert, Daniel P. Barboriak, Mark A. Rosen, Edward F. Jackson, Alexander R. Guimaraes, David E. Purdy, Thorsten Persigehl, Hendrick Laue, Marko K. Ivancevic, Gudrun Zahlmann (2014) QIBA Perfusion, Diffusion, & Flow MRI Technical Committee: Current Status Poster proceedings ISMRM meeting Milan Italy May 2014, (see www.ismrm.org).
Carolin Reischauer, Phillipp Staempfli, Thomas Jaermann and Peter Boesiger (2009) Construction of a Temperature Controlled Diffusion Phantom for Quality Control of Diffusion Measurements; Journel of Magnetic Resonance Imaging 29:692-698 describes a temperature controlled diffusion phantom using dyneema fibers which are braided strands of polyethylene
Juneja, Vaibhav, “Novel Phantoms and Post Processing For Diffusion Spectrum Imaging” (2012), UT GSBS Dissertation and Thesis (Open Access) Paper 240 .describes a crossing fiber phantom constructed of capillary filled hollow fibers of 50 micron inner diameter and 150 micron outer diameter.
Physical phantoms, as described and discussed above, provide a different balance between ground truth control and realism, to that provided by computer simulations. The above identified patents and patent applications are incorporated herein by reference and these together with the cited papers, and supporting work discussed therein, firmly establish the continued need for effective MRI phantoms for anisotropic and isotropic imaging for validating and calibrating fiber tracking technologies and systems.